OSL Image Manipulation - Revision history

Murraystevenson: /* P */

2024-08-12T00:49:43Z

← Older revision		Revision as of 17:49, 11 August 2024
Line 64:		Line 64:

	==== P ====		==== P ====
	<code>P</code> contains the position of the center of the current pixel relative to the origin of the image data window.		<code>P</code> contains the position of the center of the current pixel relative to the origin of the image [https://www.gafferhq.org/documentation/{{latestGafferVersion}}/WorkingWithImages/AnatomyOfAnImage/index.html#data-window data window].
	[[File:OslImageP.png\|none\|thumb\|900x900px\|Visualising the values of <code>P</code> as colours, the bottom left pixel has a value of (0.5, 0.5, 0) and the top right pixel a value of ( 3.5, 3.5, 0 ).]]		[[File:OslImageP.png\|none\|thumb\|900x900px\|Visualising the values of <code>P</code> as colours, the bottom left pixel has a value of (0.5, 0.5, 0) and the top right pixel a value of ( 3.5, 3.5, 0 ).]]

Murraystevenson: /* u, v */

2024-08-12T00:49:14Z

u, v

← Older revision		Revision as of 17:49, 11 August 2024
Line 68:		Line 68:

	==== u, v ====		==== u, v ====
	<code>u</code> & <code>v</code> contain the position of the center of the current pixel remapped to 0-1 across the image display window.		<code>u</code> & <code>v</code> contain the position of the center of the current pixel remapped to 0-1 across the image [https://www.gafferhq.org/documentation/{{latestGafferVersion}}/WorkingWithImages/AnatomyOfAnImage/index.html#display-window display window].
	[[File:OslImageUV.png\|none\|thumb\|900x900px\|Visualising the values of <code>u</code> & <code>v</code> as colours. The bottom left pixel has a value of ( 0.125, 0.125, 0 ) and the top right pixel a value of ( 0.875, 0.875, 0 ).]]		[[File:OslImageUV.png\|none\|thumb\|900x900px\|Visualising the values of <code>u</code> & <code>v</code> as colours. The bottom left pixel has a value of ( 0.125, 0.125, 0 ) and the top right pixel a value of ( 0.875, 0.875, 0 ).]]

Murraystevenson: /* Pixel Coordinates */

2024-08-12T00:48:26Z

Pixel Coordinates

← Older revision		Revision as of 17:48, 11 August 2024
Line 64:		Line 64:

	==== P ====		==== P ====
	<code>P</code>contains the position of the center of ~~each~~ pixel relative to the origin of the image data window.		<code>P</code> contains the position of the center of the current pixel relative to the origin of the image data window.
	[[File:OslImageP.png\|none\|thumb\|900x900px\|Visualising the values of <code>P</code> as colours, the bottom left pixel has a value of (0.5, 0.5, 0) and the top right pixel a value of ( 3.5, 3.5, 0 ).]]		[[File:OslImageP.png\|none\|thumb\|900x900px\|Visualising the values of <code>P</code> as colours, the bottom left pixel has a value of (0.5, 0.5, 0) and the top right pixel a value of ( 3.5, 3.5, 0 ).]]

	==== u, v ====		==== u, v ====
	<code>u</code> & <code>v</code> contain the position of the center of ~~each~~ pixel remapped to 0-1 across the image display window.		<code>u</code> & <code>v</code> contain the position of the center of the current pixel remapped to 0-1 across the image display window.
	[[File:OslImageUV.png\|none\|thumb\|900x900px\|Visualising the values of <code>u</code> & <code>v</code> as colours. The bottom left pixel has a value of ( 0.125, 0.125, 0 ) and the top right pixel a value of ( 0.875, 0.875, 0 ).]]		[[File:OslImageUV.png\|none\|thumb\|900x900px\|Visualising the values of <code>u</code> & <code>v</code> as colours. The bottom left pixel has a value of ( 0.125, 0.125, 0 ) and the top right pixel a value of ( 0.875, 0.875, 0 ).]]

Murraystevenson at 00:44, 12 August 2024

2024-08-12T00:44:52Z

← Older revision		Revision as of 17:44, 11 August 2024
Line 34:		Line 34:
	==== Reading channels from shaders ====		==== Reading channels from shaders ====
	The <code>InChannel</code> OSL shader can be used to read a specific channel from the processed image.		The <code>InChannel</code> OSL shader can be used to read a specific channel from the processed image.
	[[File:OSLInChannelShuffle.gif\|none~~\|frame~~\|Shuffling channels with OSLImage by reading a single channel with an InChannel shader and writing the result to other channels.]]		[[File:OSLInChannelShuffle.gif\|none\|Shuffling channels with OSLImage by reading a single channel with an InChannel shader and writing the result to other channels.\|thumb\|900x900px]]
	The <code>InLayer</code> OSL shader can be used to read the R, G, B channels of a specified image layer.		The <code>InLayer</code> OSL shader can be used to read the R, G, B channels of a specified image layer.
	[[File:OSLInLayerShuffle.gif\|none~~\|frame~~\|Reading the R, G, B channels with an InLayer shader and shuffling them to a new "shuffled" layer.]]		[[File:OSLInLayerShuffle.gif\|none\|Reading the R, G, B channels with an InLayer shader and shuffling them to a new "shuffled" layer.\|thumb\|900x900px]]

	==== Reading channels in an OSLCode node ====		==== Reading channels in an OSLCode node ====
Line 58:		Line 58:
	getattribute( "diffuse.R", diffuseR );		getattribute( "diffuse.R", diffuseR );
	</syntaxhighlight>		</syntaxhighlight>
	[[File:OSLCodeShuffle.gif\|none~~\|frame~~\|Shuffling channels using OSLCode.]]		[[File:OSLCodeShuffle.gif\|none\|Shuffling channels using OSLCode.\|thumb\|900x900px]]

	=== Pixel Coordinates ===		=== Pixel Coordinates ===
Line 65:		Line 65:
	==== P ====		==== P ====
	<code>P</code>contains the position of the center of each pixel relative to the origin of the image data window.		<code>P</code>contains the position of the center of each pixel relative to the origin of the image data window.
	[[File:OslImageP.png\|none\|thumb\|~~640x640px~~\|Visualising the values of <code>P</code> as colours, the bottom left pixel has a value of (0.5, 0.5, 0) and the top right pixel a value of ( 3.5, 3.5, 0 ).]]		[[File:OslImageP.png\|none\|thumb\|900x900px\|Visualising the values of <code>P</code> as colours, the bottom left pixel has a value of (0.5, 0.5, 0) and the top right pixel a value of ( 3.5, 3.5, 0 ).]]

	==== u, v ====		==== u, v ====
	<code>u</code> & <code>v</code> contain the position of the center of each pixel remapped to 0-1 across the image display window.		<code>u</code> & <code>v</code> contain the position of the center of each pixel remapped to 0-1 across the image display window.
	[[File:OslImageUV.png\|none\|thumb\|~~640x640px~~\|Visualising the values of <code>u</code> & <code>v</code> as colours. The bottom left pixel has a value of ( 0.125, 0.125, 0 ) and the top right pixel a value of ( 0.875, 0.875, 0 ).]]		[[File:OslImageUV.png\|none\|thumb\|900x900px\|Visualising the values of <code>u</code> & <code>v</code> as colours. The bottom left pixel has a value of ( 0.125, 0.125, 0 ) and the top right pixel a value of ( 0.875, 0.875, 0 ).]]

Murraystevenson at 00:42, 12 August 2024

2024-08-12T00:42:38Z

← Older revision		Revision as of 17:42, 11 August 2024
Line 59:		Line 59:
	</syntaxhighlight>		</syntaxhighlight>
	[[File:OSLCodeShuffle.gif\|none\|frame\|Shuffling channels using OSLCode.]]		[[File:OSLCodeShuffle.gif\|none\|frame\|Shuffling channels using OSLCode.]]

			=== Pixel Coordinates ===
			When generating patterns, it's important to know where in the image the currently shaded pixel is located. OSLImage provides two builtin variables for locating the currently shaded pixel.

			==== P ====
			<code>P</code>contains the position of the center of each pixel relative to the origin of the image data window.
			[[File:OslImageP.png\|none\|thumb\|640x640px\|Visualising the values of <code>P</code> as colours, the bottom left pixel has a value of (0.5, 0.5, 0) and the top right pixel a value of ( 3.5, 3.5, 0 ).]]

			==== u, v ====
			<code>u</code> & <code>v</code> contain the position of the center of each pixel remapped to 0-1 across the image display window.
			[[File:OslImageUV.png\|none\|thumb\|640x640px\|Visualising the values of <code>u</code> & <code>v</code> as colours. The bottom left pixel has a value of ( 0.125, 0.125, 0 ) and the top right pixel a value of ( 0.875, 0.875, 0 ).]]

Murraystevenson at 00:15, 12 August 2024

2024-08-12T00:15:23Z

← Older revision		Revision as of 17:15, 11 August 2024
Line 7:		Line 7:

	=== Writing channel data ===		=== Writing channel data ===

			==== Adding channels to OSLImage ====
	Channels are written by adding inputs to the OSLImage node by clicking on the [[File:PlugAdderIcon.png]] button in the Node Editor or by clicking or dragging a plug onto the [[File:PlugAdderIcon.png]] on the left of the node in the Graph Editor.		Channels are written by adding inputs to the OSLImage node by clicking on the [[File:PlugAdderIcon.png]] button in the Node Editor or by clicking or dragging a plug onto the [[File:PlugAdderIcon.png]] on the left of the node in the Graph Editor.
	[[File:OslImageAddInputFromNodeEditor.png\|none\|thumb\|Adding an input from the Node Editor]]		[[File:OslImageAddInputFromNodeEditor.png\|none\|thumb\|Adding an input from the Node Editor]]
Line 29:		Line 31:

	=== Reading channel data ===		=== Reading channel data ===

			==== Reading channels from shaders ====
	The <code>InChannel</code> OSL shader can be used to read a specific channel from the processed image.		The <code>InChannel</code> OSL shader can be used to read a specific channel from the processed image.
	[[File:OSLInChannelShuffle.gif\|none\|frame\|Shuffling channels with OSLImage by reading a single channel with an InChannel shader and writing the result to other channels.]]		[[File:OSLInChannelShuffle.gif\|none\|frame\|Shuffling channels with OSLImage by reading a single channel with an InChannel shader and writing the result to other channels.]]

Murraystevenson: /* Reading channels in an OSLCode node */

2024-08-12T00:12:47Z

Reading channels in an OSLCode node

← Older revision		Revision as of 17:12, 11 August 2024
Line 35:		Line 35:

	==== Reading channels in an OSLCode node ====		==== Reading channels in an OSLCode node ====
	When writing an OSL shader in an [[OSLCode]] node, Gaffer provides <code>inChannel( channelName, defaultValue )</code> and <code>inLayer( layerName, defaultValue )</code> functions to access the value of a specific channel or layer for the current pixel~~. Providing an empty <code>layerName</code> to <code>inLayer()</code> will return a color containing the value of the R, G, B channels~~.<syntaxhighlight lang="c">		When writing an OSL shader in an [http://www.gafferhq.org/documentation/{{latestGafferVersion}}/WorkingWithTheNodeGraph/TutorialUsingTheOSLCodeNode/index.html OSLCode] node, Gaffer provides <code>inChannel( channelName, defaultValue )</code> and <code>inLayer( layerName, defaultValue )</code> functions to access the value of a specific channel or layer for the current pixel. <syntaxhighlight lang="c">
	// Get the value of the "R" channel, returning 0 if the channel does not exist.		// Get the value of the "R" channel, returning 0 if the channel does not exist.
	float R = inChannel( "R", 0.0 );		float R = inChannel( "R", 0.0 );

	// Get the values of the "R", "G", "B" channels, returning black if the layer doesn't exist		// Get the values of the "R", "G", "B" channels, returning black if the layer doesn't exist
			// Providing "" as the layer name will return a color containing the value of the R, G, B channels.
	color RGB = inLayer( "", color( 0.0 ) );		color RGB = inLayer( "", color( 0.0 ) );

Murraystevenson: WIP guide to OSL Image Manipulation

2024-08-11T23:59:12Z

WIP guide to OSL Image Manipulation

New page

The [[OSLImage]] node allows the use of [https://open-shading-language.readthedocs.io OpenShadingLanguage] shaders to generate or modify pixel values in an image.
[[File:OslImageFractal.png|none|thumb|720x720px|Using an OSLImage node with a shader written in an OSLCode node to generate a fractal pattern.]]
Shaders can be built from an existing library of OSL shaders loaded via the [[OSLShader]] node, and arbitrary shader code can be evaluated via the [[OSLCode]] node. An image manipulation shader could be built entirely from existing nodes, written in a single OSLCode node, or assembled from a combination of OSL shaders and OSLCode nodes.

Shaders are evaluated per pixel in the image and typically would read that pixel value from one or more channels in the image, compute a value from those inputs and then output a new value that would replace the input pixel in an existing channel or layer, or create a new channel or layer.
[[File:OslImageLuminance.png|none|thumb|720x720px|Reading RGB values from and input image, using the OSL luminance shader to compute luminance values of those pixels, and outputting to a new channel named "luminance".]]

=== Writing channel data ===
Channels are written by adding inputs to the OSLImage node by clicking on the [[File:PlugAdderIcon.png]] button in the Node Editor or by clicking or dragging a plug onto the [[File:PlugAdderIcon.png]] on the left of the node in the Graph Editor.
[[File:OslImageAddInputFromNodeEditor.png|none|thumb|Adding an input from the Node Editor]]
[[File:OslImageAddInputGraphEditor.png|none|thumb|Adding an input from the Graph Editor]]
You can choose from common channel or layer names from the menu to write to RGB or RGBA layer, or to individual R, G, B, A channels.
[[File:OSLImageAddChannelsNodeEditor.gif|none|frame|Adding RGB and A plugs from the Node Editor.]]
You can also create arbitrary channels or layers via the <code>Custom->Channel</code>, <code>Custom->Layer</code> or <code>Custom->LayerRGBA</code> menu items. The channel or layer name can then be customised by by editing the name of the plug in the Node Editor.
[[File:OSLImageAddCustomChannelsGraphEditor.gif|none|frame|Adding a custom named "luminance" channel, and "diffuse" layer to the image.]]
{{tip | Behind the scenes, these actions are adding new child plugs to the `channels` plug of the OSLImage node.}}

{{info | The OSLImage node's channel inputs can either be a Color3fPlug or a FloatPlug, so choosing RGBA from the menu will create two plugs, a Color3fPlug for the RGB channels and a FloatPlug for the A channel. }}

Each channel or layer created provides an input connection ready to receive an OSL shader.

==== Disabling an output ====
Output layers and channels can be disabled by toggling their <code>enabled</code> plug.
[[File:OSLImageDisableChannel.gif|none|frame]]

==== Removing an output ====
Previously created output layers and channels can be removed by right clicking on the plug and selecting <code>Delete</code> from the context menu.
[[File:OSLImageDeleteChannel.gif|none|frame]]

=== Reading channel data ===
The <code>InChannel</code> OSL shader can be used to read a specific channel from the processed image.
[[File:OSLInChannelShuffle.gif|none|frame|Shuffling channels with OSLImage by reading a single channel with an InChannel shader and writing the result to other channels.]]
The <code>InLayer</code> OSL shader can be used to read the R, G, B channels of a specified image layer.
[[File:OSLInLayerShuffle.gif|none|frame|Reading the R, G, B channels with an InLayer shader and shuffling them to a new "shuffled" layer.]]

==== Reading channels in an OSLCode node ====
When writing an OSL shader in an [[OSLCode]] node, Gaffer provides <code>inChannel( channelName, defaultValue )</code> and <code>inLayer( layerName, defaultValue )</code> functions to access the value of a specific channel or layer for the current pixel. Providing an empty <code>layerName</code> to <code>inLayer()</code> will return a color containing the value of the R, G, B channels.<syntaxhighlight lang="c">
// Get the value of the "R" channel, returning 0 if the channel does not exist.
float R = inChannel( "R", 0.0 );

// Get the values of the "R", "G", "B" channels, returning black if the layer doesn't exist
color RGB = inLayer( "", color( 0.0 ) );

// Get the values of the "diffuse.R", "diffuse.G", "diffuse.B" channels, returning white if the layer doesn't exist
color diffuse = inLayer( "diffuse", color( 1.0 ) );
</syntaxhighlight>Channels can also be accessed via OSL's [https://open-shading-language.readthedocs.io/en/v1.13.9.0/stdlib.html#renderer-state-and-message-passing getattribute] function.<syntaxhighlight lang="c">
// Get the value of the "R" channel for the current pixel
float R;
getattribute( "R", R );

// Get the value of the "R" channel from the "diffuse" layer for the current pixel
float diffuseR;
getattribute( "diffuse.R", diffuseR );
</syntaxhighlight>
[[File:OSLCodeShuffle.gif|none|frame|Shuffling channels using OSLCode.]]